Method of treating metal



' Patented Oct. 11, 1938 METHOD OF TREATING METAL Samuel H. Bobrov,Gary, Ind'., assignor to American Sheet and Tin Plate Company, acorporation of New Jersey No Drawing. Application April 17, 1936, SerialNo. 75,017

2 Claims.

This invention relates to a method of treating metals, and moreparticularly those which are formed into sheets or strip.

In the manufacture of sheets or strip it is nec- 5 essary to anneal orotherwise heat-treat them in order to impart certain desirablecharacteristics. According to annealing practice, by way of example, thematerial is usually placed in a closed vessel and subjected torelatively high temperatures, such as 1000 F. to 1300 F. If sheets formthe material to be heat-treated, they are stacked in superimposedrelationship; while strip, on the other hand, is coiled. In either case,considerable difficulty is experienced in preventing sticking anddiscoloration of the material.

One method of attempting to obviate this difflculty is to coat thecontacting surfaces of the .material with a film of hydrocarbon oil.These oils necessarily leave a residue of decomposition 0 which iscarbonaceous and combustible. They are therefore only partiallyeffective depending, of course, upon their existence as a uniform film.The following factors greatly affect the film: range oftemperature-length of time of exposure to heat-character of gas withinthe closed vessel-weight, and consequent pressure of sheets orconvolutions of coil. It will be readily apparentto those skilled in theart that these factors will Widely vary and impair the effectiveness ofthe film of hydrocarbon oil.

Some mills roughen the surfaces of the sheets, or strip, in order toprovide pockets for retaining the film, and thereby obtain betterresults. However, this operation is costly and is in many instancesundesirable to the ultimate consumer.

It is one of the objects of the present invention to eliminate thesticking and discoloration of heat-treated metallic sheets and/or coils.

Another object is to provide a novel inexpensive separating. mediumwhich is comparatively indestructible and therefore applicable withequal facility to metals having smooth or roughened surfaces.

A further object is to enable the heat-treatment of sheet or coiledmetals by subjecting the same to temperatures which are considerablyhigher than those heretofore employed.

According to the teachings of the invention, I employ a metallic soapwhich is dissolved in a suitable organic solvent. The resultingsolution, when heated, leaves a separating medium which performs in themanner previously mentioned.

The metallic soap may be prepared by: (A) Agitating together a fattyacid with an aqueous solution of a water-soluble salt of the requiredmetal, which water soluble salt consists of a compound of the requiredmetal with a weak acid, such as acetic, oxalic, etc. (B) Heating freefatty or resin acids with a suitable metallic com- 5 pound, usually theoxide, hydroxide or carbonate, and less frequently the acetate, borate,oxalate, or other easily decomposed salt of the required metal. (C)Mixing of aqueous or alcoholic solutions of alkali metal or ammonium 10soaps with aqueous solutions of the salts of the required metals,whereby a relatively water insoluble metallic soap is precipitated.

The metal thus combined to form a metal ic soap may be one of any of thealkaline earth 15 metals, barium, strontium, calcium, magnesium orberyllium. But other metals, not of the alkaline earth group, are alsosuitable, thus, aluminum, cerium, chromium, cobalt, iron, manganese,

nickel, lead, titanium, thorium, 'zirconium and 20 zinc are alsosuitable and may be employed for the purpose of this invention. However,the

alkali elements, sodium, potassium, lithium, and

the ammoniacal radical NH3 are not suitable to the purpose ofapplicant's invention and are 5 therefore excluded from consideration.

The metallic soap thus obtained is dissolved in any suitable organicvolatile solvent, such as a hydrocarbon oil or oils. Much lighter-andmore volatile compounds of hydrocarbon may be em- 30 ployed than thoseheretofore used as a separating medium per se. Complete dissolution ofthe metallic soap throughout its organic solvent is effected incontradistinction over those compounds which are merely suspended in thesolvent. This obviates the necessity of continual mechanical stirringand the tendency of the soaps to precipitate out, whereby the protectingfilm would eventually be deposited on the metallic articles in globules,or segregated areas. 40

After a complete dissolution of the metallic soap in its organicsolvent, or carrier, the resulting solution may be stored indefinitelywithout deleterious efifects.

As a specific instance, I have obtained excel- 45 lent results with 1%magnesium stearate dissolved in light, white-colored 27% Baum petroleum'oil (Saybolt viscosity of to 105 at F.). The percentage of magnesiumste-' arate with respect to the light volatile oil may 50 be varied,depending on the amount of residue which is desired between the material(sheets, or coil). The solution is applied in any suitable manner.

Heretofore, the highest practical annealing 55 temperature has beenaround 1300 F., but this can easily be raised another 100 when employingthe separating medium of the invention. This higher temperature is verydesirable for most materials. v

The volatilization of the separating medium leaves an indestructibleinorganic residue which is not harmful to the smooth bright finish ofthe material and the sheets or convolutions thereof may be readilyseparated without sticking or discoloration, which could be attributedto the medium. This residue neither afiects the ap pearance of thematerial nor hinders its subsequent processing.

While I have shown and described several specific embodiments of myinvention, it will be understood that I do not wish to be limitedexactly thereto, since various modifications may be made withoutdeparting from the scope of 0 my invention, as defined by the followingclaims.

I claim:

1. The method of treating a metallic article which includes coating atleast one surface thereof with a solution comprising an organic solventand 'a soluble alkaline earth metal soap, and heat-treating saidmetallic article, to its annealing temperature thereby forming metallicoxides from the originally applied coating through decomposition by heatwhereby the sticking of said metallic article to another metallicarticle is prevented.

2. The method of treating a metallic article I which includes coating atleast one surface thereof with a solution comprising a volatile organicsolvent and a soluble alkaline earth metal soap, and heat-treating saidmetallic article, to its annealing temperature thereby forming metallicoxides from the originally applied coating through decomposition by heatwhereby the sticking of said metallic article to another metallicarticle is prevented.

SAMUEL H. BOBROV.

